Leak tightness testing method and apparatus

ABSTRACT

The disclosure relates to methods and apparatus for leak tightness testing of articles such as metal drums wherein the article is placed in a testing enclosure with a detectable gas such as nitrous oxide adjacent one closed side of the article and the space between the other side of the article and the enclosure is evacuated to a pressure lower than the gas pressure on said one closed side of the article. After the test time has passed the entire content of the evacuated enclosure space is flushed to a detector apparatus by an inert gas, preferably air, introduced into the enclosure space at a pressure higher than the pressure to which the space had been evacuated.

Waited States Patent 1 1 3,729,983 Coppens 5] May 1, 1973 I5 LEAKTIGHTNESS TESTING METHOD 3,177,704 4/1965 Stange ..73/49.3

AND APPARATUS Mattheus Johannes Martinus Coppens, Heide-Kalmthout,Belgium Inventor:

Assignee:

Filed:

App]. No.:

Inland Steel Company, Chicago, Ill.

Aug. 27, 1970 References Cited UNITED STATES PATENTS 5/1963 3/l97l5/l97l Primary Examiner-S. Clement Swisher Attorney-Wolfe, Hubbard,Leydig, Voit & Osann 5 7] ABSTRACT The disclosure relates to methods andapparatus for leak tightness testing of articles such as metal drumswherein the article is placed in a testing enclosure with a detectablegas such as nitrous oxide adjacent one closed side of the article andthe space between the other side of the article and the enclosure isevacuated to a pressure lower than the gas pressure on said one closedside of the article. After the test time has passed the entire contentof the evacuated enc|osure space is flushed to a detector apparatus byan inert gas, preferably air, introduced into the enclosure space at apressure higher than the pressure to which the space had been evacuated.

l 1 Claims, 3 Drawing; Figures Patented May 1, 1973 3,729,983

3 Sheets-Sheet 1 i 3 Sheets-Sheet Patented May 1, 1973 LEAK TIGHTNESSTESTING METHOD AND APPARATUS BACKGROUND OF THE lNVENTlON The presentinvention relates generally to leak tightness testing methods andapparatus and more parcharacterized by the rapidity and reliability ofthe test 1 to determine the presence of a leak yet wherein suchdetection is capable of determining even minute seepage or diffusionthrough faults in relatively short periods of time.

Leak tightness testing of containers, vessels, closing devices,diaphragms, and the like is of considerable importance to manufacturersand users of such products as initially produced as well as thoseproducts which are refilled or reused several times over the productlife. In shipping containers, for example, the type com monly used intransporting and storing oil products, and other liquid, semi-liquid,pulvarized, or granular substances may be reused numerous timesproviding they have not developed a leak during the transportation,storage and use normally encountered therewith. The problem also existsin pressure vessels or bottles, such for example, the type utilized forliquefied petroleum gas (LPG) that may be of the oneway type or therefillable type. However, in either instance, it is highly importantthat they be tested for leaks or seepage that could develop into a leakprior to placement in service. The reason for this is that pressurizedsubstances as well as certain solvents or inflammable fluids areextremely hazardous from the viewpoint of leakage whether in the handsof the manufacturer, supplier or consumer.

Numerous techniques have heretofore been applied for determining theleak tight integrity of containers and the like, but they are subject todisadvantages especially when attempting to ascertain minute leaks orseepages which might occur in seams, wall-joints or even areas ofweakness that may have occurred during handling or transportation. Grossleaks may be determined by visual inspection aided either by fillingwith water, or filling with a gas under pressure and immersing in water.Visual inspection has also been accomplished by building up gas pressurewithin the article aided with a soap solution spread over the article ormerely by detection of loss of pressure with a gage. Where relativelysmall leaks are involved, these techniques are not suitable due to therudimentary nature of tests and the amount if time necessary to completethem.

One approach which has heretofore been used involves placing the articleto be tested in a sealed enclosure with the pressure on one side of thearticle being higher than atmospheric pressure. The higher pressurespace includes a suitable gas which may be detected by a detectorapparatus. The gas, for example, may be nitrous oxide and the apparatusused for detection may, for example, be of the infra red spectraanalysis type which is capable of measuring the concentration of a gasby recording the optical absorption in the infra red spectrum. Theaforementioned system operates with the confined article to be testedseparating the detectable gas in the higher pressure side from theatmospheric pressure in the space provided on the side between thearticle and the enclosure. After a sufficient period of time has passedto allow for traces of gas to pass into the lower pressure space, it isevacuated into the testing apparatus to ascertain by the presence of thedetectable gas whether any leakage has occurred. Such a system presentscertain disadvantages in that it takes a fairly long period of timebefore being capable of deter- 0 mining the presence of a small leaksince evacuation of the space in which traces of the detectable gasshould appear results in a dilution of the volume presented to thedetector and small amounts of traces of gas maynot reach the detectorapparatus at all. Thus, very slight leakages may not be determined withsuch an arrangement.

Another approach to the problem of leak testing of containers likearticles and the like involves placing the article again containing thedetectable gas under pressure in a covering which is generallybellows-shaped and after a predetermined period of time has passed, theatmosphere surrounding the article within the covering is passed to thetesting apparatus by compression of the bellows-shaped covering. Thisarrangement also has certain disadvantages in that the compressiblecovering must be a considerably greater volume than the space taken upby the article to be tested which again results in some insensitivitydue to the volume of air within the covering in which any trace gaspassing from a leak will be dispersed. In addition, a significantlyhigher pressure must be built up within the article to create thenecessary differential for diffusion of the tracer gas through a faultinto the covering space which is at atmospheric pressure.

Accordingly, it is the general aim of the present invention to providemethods and apparatus which overcome all of the foregoing disadvantagesand which are characterized by their ability to more rapidly andreliably leak test articles even where very small leaks are involved,While not so limited in its application, the invention will find anadvantageous use in connection with leak testing of metal shippingcontainers or drums.

Another object of the invention is to provide improved leak testingmethods and apparatus which are extremely versatile and capable of beingutilized for a wide variety of articles and yet may be particularlysuitable for use in automated lines-for testing on a mass basis.

In another of its important aspects, it is an object of the invention toprovide improved methods and apparatus for leak tightness testing ofcontainers and the like employing a tracer detection arrangement whereinextremely small container leaks may be ascertained with a minimum timeinvolved for performing the test yet with highly reliable resultsobtained as well as the ability to pass even very small traces of gaspermeating through a leak to the detector apparatus.

An ancillary object of the invention is to provide an improved leaktightness testing apparatus which is relatively simple and may be easilymanufactured utilizing readily available and procurable components. Itis yet another object of the invention to provide apparatus whichpermits recycling of the detectable tracer gas for use with testing ofnumerous containers or similar arti cles being tested.

Other objects and advantages of the invention will become apparent asthe following description proceeds, taken in conjunction with theaccompanying drawings in which:

FIG. 1 is a diagrammatic representation of an exemplary leak tightnesstesting system in accordance with the present invention;

FIG. 2 is a graphical representation of a timing diagram for theapparatus illustrated in FIG. 1; and

FIG. 3 is a diagrammatic representation of a multiple station leaktightness testing system which is particularly suitable for testing of anumber of articles on a mass testing basis and in accordance with thepresent invention.

While the invention is susceptible of various modifications andalternative forms, specific embodiments thereof have been shown by wayof example and will herein be described in detail. It should beunderstood, however, that it is not intended to limit the invention tothe particular forms disclosed, but, on the contrary, the intention isto cover all modifications, equivalents and altematives that fall withinthe spirit and scope of the invention.

Referring now to the drawings, there is shown in FIG. 1 an exemplaryleak tightness testing apparatus, generally indicated at 10, which isparticularly suited for testing the integrity against leaks of theshipping container or drum 12 in accordance with the present invention.As best shown in FIG. 1, the exemplary apparatus includes an enclosureor covering 14 adapted to receive the drum 12 or similar article to betested, the arrangement being such that the enclosure 14 may becompletely sealed in respect to the surrounding atmosphere. Only arelatively narrow space or envelope 15 exists between the outer surfacesof the drum 12 and the inner surfaces of the enclosure 14.

For the purpose of enabling filling of the drum 12 with a suitable gasto be used in connection with the determination of leaks in the drum,there is provided an inlet conduit 16 having disposed therein a valve 18with the conduit extending through the upper end of the enclosure 14 andinto a bung hole opening 20 or the like at the top of the drum. It willbe appreciated by those skilled in the art that appropriate seals (notshown) are provided between the conduit 16, enclosure opening 17, andthe bung opening 20 into the drum 12. The opposite end of the conduit 16is connected to a reservoir 19 supplied with air and the detectable gasfrom a suitable source (not shown).

As the ensuring discussion proceeds, it will be apparent that the drumor article can be placed into the enclosure already filled with orcontaining the detectable gas under pressure in which case it isunnecessary to provide the apparatus with the gas filling arrangementdiscussed above. This, the testing of bottles such as the type employedwith liquefied petroleum may have the detectable gas added during theregular filling operation and thereafter can be tested anytime accordingto the present invention.

The particular type of detectable gas utilized is not critical to thepresent invention and any gas such as N,O, C0,, C 3,, C,H,, CH CO andvarious other gases which depending upon the particular circumstances ofthe application and type of detector apparatus being utilized is merelya matter of choice.

In order to provide for detection of the tracer gas selected, there isprovided a detector apparatus (FIG. 1) generally indicated at 22. In thepresent instance, the exemplary detector apparatus illustrated is of theinfra red spectra analysis type which detects and measures theconcentration of the tracer gas by recording its absorption in the infrared spectrum. Such apparatus is commercially available as off-the-shelfitems. Of course, other forms of detector apparatus may be utilized,such for example, as the arrangement disclosed in US. Pat. No. 2,645,117 which makes use of the change in value of a resistance in aWheatstone bridge when the detectable gas is brought into contact withthe resistance. The detector apparatus 22 as illustrated in FIG. 1includes a pair of test columns or tubes 24, 26 respectively which asmore fully described hereinafter below provide for an initial sample ofthe envelope 15 to be taken so that a comparison can be made with thetest sample thereby assuring that reliable results are obtained. Each ofthe tubes 24 and 26 are provided with inlet valves 28, 30 respectivelycoupled to a pipe 32. The pipe 32 is connected to an inlet conduit 34one end of which passes into the envelope 15 of enclosure 14.

In order to provide for evacuation of the envelope 15 as well as one orboth the test columns 24, 26 there is provided a vacuum pump 36connected to conduit 34. A valve 38 is interposed in the conduit 34 toprovide for sealing and unsealing the passageway of the conduit from theenvelope and the detector and pump. Valve 40 interposed in conduit 34between the pump and the connection pipe 32 to conduit 34 enablesconnection and disconnection of the passageway through the conduit tothe pump.

In carrying out the present invention, provision is made for flushingthe entire contents of envelope 15 into one of the detector test columnsafter the envelope has been first evacuated and a sufficient period oftime has passed for any traces of detectable tracer gas from the drumcan be present In keeping with one of the important aspects of thepresent invention, the envelope is preferably dimensioned such that itsentire volume is substantially the same as or less than the volume ofthe detector column so the entire contents of the envelope can beaccommodated by the detector without dilution of the test volume. Tothis end there is provided an inlet pipe 42 which passes into theenvelope space 15 through covering 14 adjacent the top thereof. A valve44 interposed in conduit 42 permits sealing and unsealing of thepassageway through the conduit to the envelope. The free end of conduit42 as shown in FIG. 1 may be open to the atmosphere or alternatively itmay be connected to a source of suitable gaseous medium such as airunder pressure which gas is inert with respect to the detectable tracergas. The flushing conduit 42 and the outlet conduit 34 are preferablydisposed at opposite endsof the envelope to insure that the flushing gascannot pass directly to the outlet conduit 42.

For the purpose of removing the detectable tracer gas from the drumafter completion of the test there is provided a pipe 46 having a valve47 therein coupled to conduit 16.

Preferably, provision is made for determining the presence of grossleaks in the article or drum before it is filled with the detectable gasto avoid any unnecessary waste of the gas. Thus, in the exemplaryarrangement a pressure gage 21 or any other suitable pressure sensingdevice is connected to the envelope to provide an indication that thedesired evacuated pressure is being held in the envelope.

In order to more fully understand the mode of operation of the exemplaryleak testing apparatus 10 as well as the method of the presentinvention, reference is now made to FIG. 2 wherein there is shown atiming diagram for the basic cycle of operation for the system. Prior toinitiation of the test operation, a drum 12 is first placed into theenclosure 14 which is then effectively sealed off from the surroundingatmosphere. All of the valves 18, 30, 40, 44, and 47 are closed. Valves28 and 38 are open so that the placement of the drum into the envelopecauses some of the air in the envelope to pass into the detector tube 24which will be at atmospheric pressure. This also provides for a sampleof the gas in the envelope at the inception of the test for comparisonpurposes with the sample subsequently to be tested assuring thatreliable results are obtained for each test. Valve 28 to detector tube24 is then closed and the apparatus is now in readiness for a testoperation in accordance with the present invention.

In order to initiate the testing operation, referring to FIGS. 1 and 2,conjointly, valves 30 and 40 are opened coupling the pump 36 to conduit34 thereby evacuating the envelope l5 and the second detector tube 26.At about the same time, valve 18 may be opened provided that no grossleaks have been sensed by pressure gage 21, and a mixture of thedetectable gas and air flows into the drum 12 from reservoir 19. Valves28, 44 and 47 remain closed. When a sufficient degree of vacuum has beendrawn and held in the envelope which occurs after a predetermined timedepending'upon the volume of the envelope and the capacity of the vacuumpump, valve 38 is closed. The n pump 36 is still operated to evacuatethe detector tube 26 to a still lower pressure. At about the same timevalve 18 is closed since the pressure in the drum will have achieved asufficiently high enough pressure for the test purposes. Shortlythereafter, valves 30 and 40 will be closed to disconnect the pump andseal off the test column 26 at its now lower pressure.

When the valve 38 has been closed the waiting time for-allowing anydetectable gas to pass through any drum leak has begun. During this timetoo, a check may be made for larger leaks by taking pressuremeasurements in the envelope.

In keeping with the invention, at the end of the waiting time, thevalves 30, 38 and 44 are opened. Air or other suitable inert gasentering the envelope adjacent the top through conduit 42 flushes outall of the gas present in the envelope causing the latter to flowthrough conduit 34 and pipe 32 into detector tube 26. The detectorapparatus 22 will show if there was a leak when relatively moredetectable gas is in tube 26 than in tube 24. During this time valve 47in conduit d6 opens to release the pressure and detectable gas remainingin the drum to restore it to atmospheric pressure for removal from theenclosure. The gas in the drum may be discharged to the atmosphere orprovision may be made for returning it to the reservoir 19 for reuse ina subsequent test.

Upon completion of the flushand restoration of the drum pressure toatmospheric pressure, valves 30, 44 and 47 are closed thus returning thetesting apparatus to its initial state in readiness for a subsequenttesting operation on the next drum. The drum l2 may now be removed fromthe enclosure and a next drum to be tested placed in the enclosure.While the drum changing takes place, the detector apparatus 22 completesits determination as to whether or not any leaks are present.

Referring now to FIG. 3, a multiple station testing arrangement has beendepicted. In this instance, the exemplary arrangement which enables leaktightness testing of drums or the like on a high speed production basisincludes a plurality of enclosures 50-53, there being four in number toenable testing of drums 54-57, respectively. Each enclosure has an inletconduit 58-61 with respective valves 62-65 for filling the drums withthe detectable gas from reservoir 66. Flushing conduits 67-70, alsohaving valves therein, are provided adjacent to the top of each of theenclosures.

Outlet conduits 71-74 for each of the enclosures, each having a pair ofvalves 75,76 (a-c) contained therein couple the enclosures to a singlevacuum pump 77 for evacuating the envelopes surrounding the drums.

For the purpose of analyzing the gases of each of the enclosureenvelopes, there is in this instance provided a pair of detectors 78, 79similar to the detector 22 of FIG. I. Since the exemplary system of FIG.3 utilizes two detectors, pipes 80, 81 connect detector 78 to conduits72, 74 of enclosure 51, 53, respectively, and detector 79 through pipes82, 33 is connected to enclosures 50, 52 via respective conduits 71, 73.This arrangement permits sequential operation of the system by testingand loading and unloading drums taken two at a time.

For the purpose of removing the detectable gas from the drums after thetest thereby restoring the internal pressure to atmospheric pressure andrecycling the detectable gas back to the reservoir 66 there is provideda pipe line 84 having a compressor pump 85 interposed therein with thepipe line 84 being attached via individual pipes 87-90 connectedrespectively to inlet conduits 58-61 of the enclosures 50-53. Valves91-94 interposed in each of the pipes 87-90, respectively, permitclosing-off of the return lines to the suction side of the pump 85.

Keeping in mind the previous operational description of the apparatus 10shown by way of example in FIG. 1, it will be appreciated that a typicalcycle of operation of two of the test enclosures will be the same asdescribed for FIG. 1, each test station operating with one of thedetectors 78 and 79. To this end, at initial start-up with a drum loadedin each of the enclosures, all of the valves will be closed exceptvalves 75, a in outlet conduits 71,72 and the valves for one of the testcolumns in each of the detectors (not shown). Valves 75b and 75c ofenclosures 52 and 53 are closed since in this instance they are notinvolved. in the initial test. The valves of the aforesaid ones of thetest columns in each of the detectors are closed and valves 76- and 62of enclosure 50 as well as valve 760 and 63 of enclosure 5i are opened.Also, the valves for the other test columns of each of the detectors 78,79 are opened.

Thus, simultaneous filling of drums 54 and 55 occurs with the evacuationof the envelopes of enclosures 50 and 51 and the two test columns ofdetectors 78 and 79. When the appropriate degree of vacuum in enclosures50, 51 is reached and the drums 54, 55 are filled with the detectablegas, valves 62,63, 75 and 75a are closed. Valves 76 and 76a remain openas do the valves to the test columns until the latter are evacuated to alower pressure than the envelopes of enclosures 50 and 51, after whichthese valves are closed. Upon completion of the waiting time for thetest, valves 67 and 68, 75 and 75a are all opened to flush the gas inenvelopes of enclosures 50 and 51 to their respective test columns.Valves 91 and 92 are opened at this time to return the detectable gasand their respective enclosures 52 and 53 may be evacuated in readinessfor completion of the test therewith as soon as the detectors are freefrom the test conducted on drums S4 and 55.

After completion of the test on the first two drums valves 91 and 92 areclosed and drums 54 and 55 can be removed with two new drums beingplaced in the enclosures 50 and 51 to be prepared for the next sequence.In the meantime, assuming that the detectors 78, 79 have been cleared,the same test procedure can be followed with respect to the drums 56 and57 in enclosures 52 and 53.

It will be appreciated from the foregoing that there has herein beendisclosed relatively simple and reliable methods and apparatus which arehighly effective in leak testing metal shipping containers or drums on ahigh speed production basis. This advantageous result is achieved by thecomplete flushing of the envelope surrounding the drum into the detectortest column so that any traces of the detectable gas that might havefiltered through even a very small leak in the container walls, jointsor seams may be sensed by the detector apparatus. When utilizing adetector which can sense differences of 10 to 100 ppm of detectable gas,such as nitrous oxide in air, the present system is able to detect leakson the order of one cubic centimeter/minute across a pressure differenceof one atmosphere.

The method and apparatus in accordance with the present invention mayalso be applied with numerous other articles besides containers or drumswithout cleparting from the invention. Thus, in accordance with thepresent method, the tightness of an article wall, weld seam or the likecan be tested by confining the article in an enclosed space, providing adetectable gas under pressure in the portion of the space on one side ofthe article and after a sufficient predetermined time has passed for anygas to permeate through a leak has taken place, then flushing the gascontents from the evacuated space side into a detector apparatus.

4 I claim as my invention:

1. The method of leak tightness testing of articles wherein a closedspace containing a pressurized detectable gas is presented adjacent oneside of the article and an enclosed space is adjacent to the oppositeside of the article, comprising the steps of, evacuating said enclosedspace adjacent said opposite side of the article to a pressure lowerthan the pressure in the space ad jacent the side of the articlecontaining the detectable gas, permitting the passage of a sufficientpredetermined time to allow said detectable gas to permeate leaksthrough in said article, and then thereafter flushing the gaseouscontents from said previously evacuated space by introduction of agaseous medium inert to the detectable gas and at a pressure higher thanthe pressure to which said space was evacuated, directing the flushedcontents of said evacuated space to the detector apparatus fordetermining the presence of said detectable gas as an indication ofa'leak in the article, and evacuating the detector apparatus to a lowerpressure than that of the evacuated space adjacent said article beforedirecting the flushed contents of the evacuated space to the detectorapparatus.

2. The method of leak tightness testing of articles wherein a closedspace containing a pressurized detectable gas is presented adjacent oneside of the article and an enclosed space is adjacent to the oppositeside of the article, comprising the steps of, evacuating said enclosedspace adjacent said opposite side of the article to a pressure lowerthan the pressure in the space adjacent the side of the articlecontaining the detectable gas, permitting the passage of a sufficientpredetermined time to allow said detectable gas to permeate throughleaks in said article, and then thereafter flushing the gaseous contentsfrom said previously evacuated space by introduction of a gaseous mediuminert to the detectable gas and at a pressure higher than the pressureto which said space was evacuated, and introducing at least a portion ofthe contents evacuated from said space adjacent said article as areference sample into the detector apparatus for subsequent comparisonwith said flushed contents received from said evacuated space as thetest sample.

3. The method of leak tightness testing of metal drums and the like,comprising the steps of, placing said drum into an enclosure wherein aclosed space is defined between the inner walls of the enclosure and theouter walls of the drum, evacuating said closed space between saidenclosure and said drum to a first pressure, filling said drum with adetectable gas from a source to a second pressure, within said drumhigher than said first pressure in the closed space, allowing apredetermined time to pass for traces of the detectable gas to permeatethrough a leak in said drum into said evacuated closed space, flushingthe contents of said evacuated space by introduction of a gaseous mediuminert to the detectable gas and at a third pressure higher than thefirst pressure of said evacuated space and directing said flushedcontents of the evacuated space into a detection apparatus fordetermination of traces of the detectable gas indicative of a leak.

4. A method in accordance with claim 3 wherein said detection apparatusis evacuated to a fourth pressure lower than the first pressure to whichsaid space is evacuated prior to receiving the flushed contents fromsaid evacuated space.

5. A method in accordance with claim 3 wherein substantially all theremaining portion of said detectable gas in said drum is returned tosaid source.

6. A method in accordance with claim 4 wherein at least a portion of thecontents of said closed space prior to evacuation thereof is directed tosaid detector for comparison with said flushed contents received by thedetector from the evacuated closed space.

7. A method in accordance with claim 3 wherein said closed space is ofsubstantially no greater volume than the detector test volume so thatsubstantially all the contents of the closed space is directed into thedetector.

8. Apparatus for leak tightness testing of drums and the like comprisingin combination, an enclosure adapted to sealingly receive said drum,said enclosure being dimensioned such that a closed space is definedbetween the drum and enclosure, a source of detectable gas, means forfilling said drum in said enclosure with said detectable gas, detectormeans for determining the presence of said detectable gas, scalablepassage means connecting said detector with said closed space, means forevacuating the contents of said closed space to a pressure lower thanthe pressure of said detectable gas within the drum, means for flushingthe contents of said evacuated space into the detector means byintroduction of a gaseous medium inert to the detectable gas and at apressure higher than the pressure of the evacuated space, and means forcoupling said evacuating means with the detector so that said detectormay be evacuated along with said closed space.

9. Apparatus as claimed in claim 8 including means for disconnectingsaid evacuating means from said closed space while retaining theconnection between the vacuum source and said detector means so that thelatter is evacuated to a lower pressure than the pressure in said closedspace.

10. Apparatus for leak tightness testing of drums and the like,comprising, in combination a plurality of enclosures adapted tosealingly received individual drums, said enclosures being dimensionedsuch that a space is defined between the drums contained therein and theenclosures, a source of detectable gas, means for selectively fillingsaid drums in said enclosures with said detectable gas, a plurality ofdetector means for determining the presence of said detectable gas,sealable passage means connecting said] detectors with said enclosurespaces, means for selectively evacuating the contents of said enclosurespaces to pressures lower than the pressures of said detectable gas withthe drums, means for selectively flushing the contents of individualones of said evacuated spaces into different ones of said detector meansby introduction of a gaseous media inert to the detectable gas and apressure higher than the pressure of the evacuated space and means forsequentially testing certain ones of said drums and changing theremaining drums for subsequent tests.

11. Apparatus as claimed in claim 10 including means for selectivelyreturning the substantially all remaining portions of said detector gasfrom said drums to said source.

1. The method of leak tightness testing of articles wherein a closedspace containing a pressurized detectable gas is presented adjacent oneside of the article and an enclosed space is adjacent to the oppositeside of the article, comprising the steps of, evacuating said enclosedspace adjacent said opposite side of the article to a pressure lowerthan the pressure in the space adjacent the side of the articlecontaining the detectable gas, permitting the passage of a sufficientpredetermined time to allow said detectable gas to permeate leaksthrough in said article, and then thereafter flushing the gaseouscontents from said previously evacuated space by introduction of agaseous medium inert to the detectable gas and at a pressure higher thanthe pressure to which said space was evacuated, directing the flushedcontents of said evacuated space to the detector apparatus fordetermining the presence of said detectable gas as an indication of aleak in the article, and evacuating the detector apparatus to a lowerpressure than that of the evacuated space adjacent said article beforedirecting the flushed contents of the evacuated space to the detectorapparatus.
 2. The method of leak tightness testing of articles wherein aclosed space containing a pressurized detectable gas is presentedadjacent one side of the article and an enclosed space is adjacent tothe opposite side of the article, comprising the steps of, evacuatingsaid enclosed space adjacent said opposite side of the article to apressure lower than the pressure in the space adjacent the side of thearticle containing the detectable gas, permitting the passage of asufficient predetermined time to allow said detectable gas to permeatethrough leaks in said article, and then thereafter flushing the gaseouscontents from said previously evacuated space by introduction of agaseous medium inert to the detectable gas and at a pressure higher thanthe pressure to which said space was evacuated, and introducing at leasta portion of the contents evacuated from said space adjacent saidarticle as a reference sample into the detector apparatus for subsequentcomparison with said flushed contents received from said evacuated spaceas the test sample.
 3. The method of leak tightness testing of metaldrums and the like, comprising the steps of, placing said drum into anenclosure wherein a closed space is defined between the inner walls ofthe enclosure and the outer walls of the drum, evacuating said closedspace between said enclosure and said drum to a first pressure, fillingsaid drum with a detectable gas from a source to a second pressure,within said drum higher than said first pressure in the closed space,allowing a predetermined time to pass for traces of the detectable gasto permeate through a leak in said drum into said evacuated closedspace, flushing the contents of said evacuated space by introduction ofa gaseous medium inert to the detectable gas and at a third pressurehigher than the first pressure of said evacuated space and directingsaid flushed contents of the evacuated space into a detection apparatusfor determination of traces of the detectable gas indicative of a leak.4. A method in accordance with claim 3 wherein said detection apparatusis evacuated to a fourth pressure lower than the first pressure to whichsaid space is evacuated prior to receiving the flushed contents fromsaid evacuated space.
 5. A method in accordance with claim 3 whereinsubstantially all the remaining portion of said detectable gas in saiddrum is returned to said source.
 6. A method in accordance with claim 4wherein at least a portion of the contents of said closed space prior toevacuation thereof is directed to said detector for comparison with saidflushed contents received by the detector from the evacuated closedspace.
 7. A method in accordaNce with claim 3 wherein said closed spaceis of substantially no greater volume than the detector test volume sothat substantially all the contents of the closed space is directed intothe detector.
 8. Apparatus for leak tightness testing of drums and thelike comprising in combination, an enclosure adapted to sealinglyreceive said drum, said enclosure being dimensioned such that a closedspace is defined between the drum and enclosure, a source of detectablegas, means for filling said drum in said enclosure with said detectablegas, detector means for determining the presence of said detectable gas,sealable passage means connecting said detector with said closed space,means for evacuating the contents of said closed space to a pressurelower than the pressure of said detectable gas within the drum, meansfor flushing the contents of said evacuated space into the detectormeans by introduction of a gaseous medium inert to the detectable gasand at a pressure higher than the pressure of the evacuated space, andmeans for coupling said evacuating means with the detector so that saiddetector may be evacuated along with said closed space.
 9. Apparatus asclaimed in claim 8 including means for disconnecting said evacuatingmeans from said closed space while retaining the connection between thevacuum source and said detector means so that the latter is evacuated toa lower pressure than the pressure in said closed space.
 10. Apparatusfor leak tightness testing of drums and the like, comprising, incombination a plurality of enclosures adapted to sealingly receivedindividual drums, said enclosures being dimensioned such that a space isdefined between the drums contained therein and the enclosures, a sourceof detectable gas, means for selectively filling said drums in saidenclosures with said detectable gas, a plurality of detector means fordetermining the presence of said detectable gas, sealable passage meansconnecting said detectors with said enclosure spaces, means forselectively evacuating the contents of said enclosure spaces topressures lower than the pressures of said detectable gas with thedrums, means for selectively flushing the contents of individual ones ofsaid evacuated spaces into different ones of said detector means byintroduction of a gaseous media inert to the detectable gas and apressure higher than the pressure of the evacuated space and means forsequentially testing certain ones of said drums and changing theremaining drums for subsequent tests.
 11. Apparatus as claimed in claim10 including means for selectively returning the substantially allremaining portions of said detector gas from said drums to said source.